1. Field of the Invention
This invention relates to a preparation of pyruvate oxidase with excellent thermal stability, to an analytical method that makes use of this preparation, and to analytical reagents for use in this analysis.
2. Description of the Prior Art
Pyruvate oxidase is classified as EC 1.2.3.3. It is an enzyme that catalyses a reaction that produces acetyl phosphate, carbon dioxide, and hydrogen peroxide from pyruvic acid, inorganic phosphate, and oxygen. Pyruvate oxidase can be used to measure the amount of pyruvic acid in, for example, blood or urine samples, or to measure the enzyme activities of glutamic-pyruvic transaminase, glutamic-oxaloacetic transaminase, lactate dehydrogenase, pyruvate kinase, L-amino-acid oxidase, etc.
It is known that pyruvate oxidase is produced by a variety of microorganisms. For example, it is known to be produced by Lactobacillus delbrueckii (B. Maruo, N. Tamiya, compilers, Enzyme Handbook (in Japanese), Asakura Bookstore, publisher), Lactobacillus plantarum (J. Bacteriol., 160, 273-278 (1984)), microorganisms of the genus Pediococcus, Streptococcus, and Aerococcus (all of the above disclosed in Laid Open Patent Publication No. 58-40465), microorganisms of the genus Leuconostoc (disclosed in Laid Open Patent Publication No. 59-159777), etc. However, the pyruvate oxidase produced by all of these microorganisms has poor resistance to heat (to less than 40.degree. C.). Thus, problems with thermal stability can arise during, for example, the measurements mentioned above of pyruvic acid or other enzymes.